How The Volcanic Flow Destroyed Pompeii | Pompeii's Pyroclastic Flow | Timeline

[Music] in the year 79 ad the legendary Italian volcano Mount Vesuvius erupted [Music] [Music] it buried the nearby roman town of pompeii just over a thousand bodies have been found in the partly excavated streets and houses [Music] visitors are still told that the victims were all crushed by a huge deluge of rock but there is a mystery here few of the bodies show any sign of damage or violence nor did they succumb to boiling hot lava that would have taken a week to reach them plenty of time in which to escape their town is decimated yet the bodies seem to be virtually intact now forensic science is rewriting history in Pompeii there's evidence of one of the rarest of all volcanic phenomena the latest data completely disproved the traditional explanation for the first time it's possible to create the definitive hour-by-hour account of that terrible day and to answer the riddle of Pompeii [Music] [Music] Mount Vesuvius and old Pompeii are now both engulfed by the urban sprawl of Naples [Music] Vesuvius is still a destroyer it's erupted over 30 times in the last two thousand years for centuries lava has regularly flowed down the mountain and damaged the towns beneath [Music] professor Harold sa Goodson is the foremost authority on Vesuvius he studied its every eruption including the most recent in 1944 but the new cone of Vesuvius is right behind me here that's the active cone has been build-up since the formation of the caldera and that cone continues to erupt as recently as 1944 when this lava flow came down the slope from the crater and flowed down here down into the caldera I said accumulated there it continued to float down towards the west and then down off the volcano into the into the built-up areas following down one of the major valleys are the issues from the volcano and there it flowed into and through the city of San Sebastiano destroying many houses and causing tremendous damage however while it brought heartache to thousands only 20 empty actually died it is very rare that people get killed by lava flows because simply you have a lot of time to move out of the way but you lose your house is those you plant lose your fields and so the destruction is very extensive but the death toll is almost nil [Music] so why was the death toll so high during Vesuvius his most famous eruption in 79 AD it was 1500 years before someone stumbled on the first clue [Music] in 1594 the architect Domenico Fontana supervised the digging of a tunnel through the area to divert water to this munitions factory which is still in use his workmen hid painted walls bearing the inscription Pompeii but it was only in 1748 that excavation started in earnest [Music] soon workmen were pulling out treasure after treasure [Music] the excavators were surprised at how easy it was to dig for the volcanic material that covered the town was not rock hard black lava but lava smashed into billions of particles of dust and pumice and buried in it lay the strongest clue to the mystery in 1863 the archaeologists Duceppe Fiorelli noticed that the skeletons of the Pompeians were usually found inside hollow cavities he decided to pour plaster into them and the shapes they produced were amazing [Music] buried under metres of volcanic material the soft tissues of the bodies had rotted away leaving only the bones and an exact hollow impression of the corpse [Music] people marveled at the sleeping dead but scientists were baffled of the 1,000 bodies exhumed few had horrendous injuries few were trapped or crushed it's only now with the invention of 3d MRI scanning that strong clues to the cause of death can be gleaned at the University of Naples professor Francesco Sasso has scanned five skeletons found just outside Pompeii during recent road widening if you look at this skull there's an anomaly we found in the left maxillary sinus tubes a big plug of white powdery material in particular if you look closely you can see these white particles here it looks very like dust it seems that the victims were exposed to extremely dusty air but could that really have accounted for so many deaths [Music] haroldo Sigurdsson has tried to answer this riddle for the last 20 years he's conducted an exhaustive study of the rock strata at many sites around vesuvius and has just completed his calculations we are here at the plant is up just to the southwest of the volcano it's an imperial villa but it's also a place where we have a complete stratigraphy all of the layers are represented here Hato plant is from the 79 eruption now I'm standing on the Roman soil or surface ground level and here's the first time this fall represented by this layer Sigurdsson has established that all of this material fell from the sky like rain could the Pompeians simply have been buried alive to find out more sigurðsson first turned to the only eyewitness account of the eruption that of writer Pliny the Younger pliny tells us that he his mother and his uncle Pliny the Elder were 30 kilometers west of Vesuvius at the port of my scene on his uncle was the senior official in the area and commander of the Roman Navy Pliny the Younger z' account focuses on the heroic death of his uncle but he also provides vital clues to the mystery crucially he times the start of the eruption at 12:00 noon on the 24th of August at noon my mother drew his attention to a cloud of unusual size and appearance [Music] he called for his shoes and climbed up to a place which would give him the best view of the phenomenal it's general appearance can be best expressed as being like an umbrella pine for it rose to a great height on a sort of trunk and then split off into branches I imagine because it was thrust upwards by the first blast and then left unsupported as the pressure subsided sometimes it looked white sometimes blotched and dirty Plenty's description of a column of cloud stretching many kilometers above him has perplexed scientists could the eruption really have been this big Sigurdsson has measured the total amount of material the volcano dropped in the area and believes that Pliny was absolutely correct rather than a slow lava flow the 79 AD eruption was an event that only happens every two to five thousand years a massive explosion of molten rock a single volcano has many different styles of eruption as Miss Lewis does we know that the Soviets produces lava flows signifying that the presence of mark millar is poor in gases it produces very explosive eruptions some of the most explosive on earth signifying that it also has magnets that are very gas rates under Vesuvius is a magma chamber an underground tank of molten rock from the crater above Sigurdsson has calculated it is five kilometers in diameter and three kilometers down as it fills up it causes earthquakes and heating of the groundwater the rock above it eventually splits a fish air appears and a thin column of magma makes its way to the surface if it leaks out slowly it results in a lava flow [Music] but in 79 ad the column couldn't squeeze out of the surface because of dense rock formations over hundreds of years the pressure built up if you have a break of hundreds of years or an extensive break of no activity magma is still coming up into the reservoir and as it accumulates in the reservoir that magma undergoes certain chemical changes that lead to a buildup of gases in the magma at noon on the 24th of August the buildup of gases cracked the volcano's cone the trapped molten rock shot up into the air fragmented and cooled into billions of particles of dust and pumice high-altitude winds blew it to the southeast within minutes Pompeii was at the center of the deluge but this isn't what killed the victims [Music] the eruption of Vesuvius in 79 AD was the biggest for 4000 years geological data shows that had ejected 10,000 tons of material every second such was its power that rock flew many kilometres up into the sky and then hurtled down towards Pompeii however Professor seiga-san's theory is that most of the population survived the downfall because the material is too light to kill them for the magma is moving up from great depth it's subject to a great pressure deep in the earth all the gases are pressed into the magma into the liquid but when the liquid moves higher the gas has come out in their form bubbles and the bubbles get bigger and they get more numerous and they they effervesce if you like and it forms a foam the magma turns into foam the foam is filled with gas cavities that are filled with steam and that foam is then ejected explosively and breaks up solidifies in the in the atmosphere the the magma of the liquid surrounding the bubbles forms glass volcanic glass and what we end up with is pumice very light weight material low density floats on water but it is rock it's rock full of bubbles indeed circuits and is able to calculate how quickly the pomace dropped by comparing the crater size - how far Palace traveled he can show that it fell at around 20 centimeters an hour and according to Pliny the Younger people were able to protect themselves as a protection against the falling objects they put pillows on their heads tied down with cloth two writers 2,000 years apart show that the population of Pompeii should simply have been able to walk away so why didn't they all leave it seems at first people did not know what was happening [Music] educated Romans certainly knew what volcanoes were Pliny the Elder wrote about Mount Etna in Sicily and was aware of the existence of lava flows he would also have read the engineer Vitruvius who wrote fifty years before him he believed for sooo vyas was a volcano but that it was dormant and therefore no cause for concern [Music] at that time the crater of Vesuvius was described as being draped with vegetation and and difficult to access also we have evidence from frescoes so there's a famous fresco I was found in Pompeii that shows the volcano as being forested this heavy vegetation indicates that Vesuvius hadn't erupted at all for a long time modern geological studies suggest for around 400 years but while they'd never seen or heard of Vesuvius erupting the Pompeians were no strangers to earthquakes in 62 AD one nearly wiped out the town historian ray Lawrence has studied the houses of the town and the surrounding area of campaign iya campaigner is associate hill ways with earthquakes so there's a certain amount of yes it's campaign eeeh so there are earthquakes so off the 880 62 earthquake Seneca would tell us that somebody's mad if they want to give up coming to Pompeii for instance because they're frightened of earthquakes you'd say that's the wrong motive in fact archaeologists have found strong evidence of earthquake activity in the weeks leading up to the eruption the villa castilla monte on the main shopping street was a typical large townhouse which had suffered recent damage before the 24th of August ad 79 this area had suffered very badly from earthquakes and there was a need to reconstruct things this is a house where a lot of change has happened because we're not just dealing with one house we're dealing with a block of houses which are all interconnected so different things are happening in different parts of the house it's thought that in the back for instance and painters had been working that morning because there's a Paint Pot found in the corner and it's not just the Villa Castilla Monte there are patched up masonry cracks and patched up frescoes all over Pompeii the Pompeians may not have known that imminent volcanoes also cause tremors when the huge eruption of rain and pumice started they must have been scared but their experience of earthquakes told them to sit it out rather than fleeing within the structure of the eruption itself that there's a certain amount of waiting and seeing and then somebody comes to tell you you're an idiot unless you believe and even people like penny the younger sits down and reads from Livy Livia's history of Rome rather than leaving the building and it's only when one of his uncle's friends who's from Spain comes to see him and says look why don't you leave that's the obvious thing to do at this moment in time the building will fall apart and you should simply go a new mapping study by Professor de Corollas has analysed all the old excavation records he has plotted what bodies were found where and it confirms that people did show a degree of hesitation before leaving it all could all get for somebody like me what we can say is it the first natural reaction of those who had relatives or friends in the city must have been to go and look for them as well as to go and look for the most precious objects in their homes in order to take them away Susy que viene la casa port Olivia this is now scientifically confirmed as many human bodies had by the many pressures of a novena sea Gnomeo subjective rates yossi queen the key therefore whoever did whoever managed to escape must have thought of taking away their personal properties we also find and this is quite obvious their house key I mean many bodies were found with the iron house key of their own homes so those who ran away first locked their houses and then left we know this for sure this early hesitation was to prove fatal [Music] circuit's ins calculations showed that the rate at which the volcano ejected material actually increased in the first few hours this pumice fault begins to form probably around noon and unless you see it's getting coarser the cautioning of the pumice fall is due to increased intensity of the eruption the eruption is getting more violent there's more energy there's a higher rate of magma initially the magma is coming out at the rate of about a million kilograms per second towards the upper part of this layer we call this the white pumice towards the upper part of it it was coming out about 10 million kilograms per second so there's an increased tenfold increase in the rate of flow of the magma out of the volcano this particular states of the eruption we call the plinian stage in honor of the plea knees they've the plane of the younger was the first one to document and observe this type of activity and you observed an eruption column that went up to great height in the atmosphere actually we've done some modeling and investigations on this particular deposit and and the phase of the eruption and we know that it started off as about a 17 kilometers high eruption column and we went up to about 32 kilometers in fact the heat generated by the eruption was so great that the pumice was carried 30 kilometers above the Earth's surface three times higher than airliners fly with Pliny providing the start time of new say blitzen's flow rate data show that by 4:00 in the afternoon Pompeii was smothered in a blanket of pumice nearly a meter deep by this stage the roofs all over the town were under unbearable pressure [Music] between them and the end of the day almost all of the 20,000 people archaeologists estimate lived in the city did finally live but 1044 bodies have been recovered within the city walls why did they and perhaps even more stay new findings suggests that not everyone may have been able to flee professor's Chaparro low and casino have been able to extract DNA from 13 skeletons found at a house in the town's main shopping street the cars are poly bo the results show that there were strong bonds of attachment lovers family in the people from Polybius house there were two people with the disease spina bifida although we can't say if it would have affected him in any way but there are telltale signs for why they may have stayed one of these people was a young pregnant woman at the end of her term very close to giving birth and this perhaps could be the reason they decided not to flee to stay in the house and to hope to save themselves maybe she lives in Gaza the spirit is a lasting one decides to stay because one lover is sick and they can't flee because they want to remain together that seems reasonable to me they avoid sa vision these pictures show some of them in the position they were found two of them in particular these two are holding hands this of course suggests a very strong family bond we think that one of the two is a teenager so he's probably holding his father's hand in addition to DNA testing professor Sasso has found that in the group he has analyzed there was someone who may have been in too much pain to flee well this subject suffered from toothache a serious toothache in the roots and he also suffered from an abscess of the maxillary sinus it's one of those tooth aches where half the face is swollen up and in great pain that's one reason he may have stayed if there were other reasons we don't know but he must have been somebody with a strong resistance to pain he probably was a soldier or a gladiator this perfectly healed wound it's obviously a sword wound shows he was a fighter a tough man whether they were forced to stay or whether they fled the population of Pompeii must have feared the worst bizarre weather could only have added to the sense of doom follow the elements are working against you there continuous lightning strikes because one of the properties of a big explosive eruption like this is that it basically short circuits the electrical conditions between the earth and the upper atmosphere and that produces almost continuous lightning in the in the eruption cloud so that would have been a frightful scene pliny the elder's predicament illustrates the growing chaos he tried to lead the Roman Navy to the coast near Pompeii to evacuate refugees but they were beaten back by huge flows of floating pumice he eventually landed at stabby eye and took refuge with his friend pompon Yanis but soon the rescuer became a hostage finding the door of his room blocked by the palace wall they debated whether to stay indoors or take that chance in the open for the buildings were now shaking with violent shocks and seemed to be swaying to and fro as if they were torn from their foundations outside on the other hand there was the danger of falling pumice stones even though these were light and porous however after comparing the risks they chose the latter from Pliny the Younger account it seems that his uncle Pliny the Elder made it to the relative safety of stabby I be touched by the late evening but by that stage around 9 or 10 p.m. the eruption was at its most powerful in Pompeii the pumice was getting very deep let's look at the pumice that has accumulated here to a height of or a thickness of almost two and a half meters of course we begin here around noon on the 24th on the ground on the Roman ground that I'm standing on and here it was covered with pig arm for us and then during the early stages of the eruption we have an accumulation of the of the white pumice ball falling out of the sky and accumulating here gradually during the afternoon of the 24th and around our late afternoon or evening to begin to see a change in the color of the humus ball turning darker gray and that continues to fall up to about 3 or 4 in the morning on the next day when the first surge reaches Pompeii and that is that dark band what we see on the top of this excavation with no lava flows and only a few large rocks in the deposit scientists have naturally assumed that this never-ending cascade of pumice is what eventually overcame the victims but astonishingly circuits and findings show this is not the case we see the tremendous effects of that sorts on the people and we see where the people where in Pompeii they weren't down here at ground level they weren't walking around they weren't being buried by the pumice fall but rather they were walking on top of it and we see the remains right here on top [Music] amazingly sigurðsson speery is that just about everyone survived the constant pumice fall by continuing to walk on top of the ever-growing carpet of rock their cause of death was about to arrive [Music] when the eruption finally subsided Pompeii was buried in four meters of pumice centuries later as the excavations commenced a pattern started to emerge a few bodies were found deep down indicating they died early on they appeared to have been hit by falling masonry [Music] but the vast majority were found much higher up near the surface indicating they died later in fact they were all founded exactly the same level strongly suggesting they died at virtually the same time and none of them had any apparent injuries I think they died for lack of oxygen by suffocation that's oficio by suffocation one of them had his mouth open it was shocking because if you look at the excavation pictures when the skeleton was found his mouth was wide open for lack of oxygen family value same thing with the horses their head was turned they were on the floor but their mouth was turned up so they clearly lacked oxygen the position of the bodies is powerful evidence it strongly suggests that the victims died by inhaling something lethal but what some of the mouths of the victims of Pompeii seems to confirm this hypotheses some of them are lifted up on their arms as if craning their necks upwards towards some slightly cleaner air we're still waiting to prove this but they must have had some serious breathing difficulties so what could have made the air suddenly so deadly if breathing dust had been the cause surely they would all have died at different times because of different lung capacities and hiding places it is only now after 20 years of painstaking analysis that Sigurdsson can prove what really happened Vesuvius generated what is now known as a pyroclastic surge [Music] I was very lucky to be involved in the research on a very similar eruption that took place in 1982 and I was the eruption of el chichon volcano in Mexico that killed about 2,000 people and in that eruption several surges were produced that were witnessed and people were killed in those and I I was on the scene there about two days after the eruption and was able to study those surges and they look exactly like these surges sigit soms identification of surge layers in the rock at Pompeii was the answer scientists had been waiting for not every volcano develops a surge it's a complex phenomenon where the eruption can be seen like a jet engine the power it's generating is keeping the whole column up in the air but as the crater around the eruption starts to cave in it interrupts the flow of power the column briefly collapses the result is a falling cloud that hits the ground at over 200 kilometres an hour it spreads out over a vast area like a giant dust filled hurricane knocking over walls destroying everything in its path the mystery of the search is that as it settles it leaves nothing but a very thin layer of ash which is quickly buried by further palace wall over here we go to the wall of the deposit where we can see the other surges quite clearly we have the fall deposit the pomace vault deposit here quite large promises because we're fairly close to the volcano and the first search forming this thin layer followed by another stage of fallout so the first search represents the first collapse of the eruption column instead of a very high plenty on eruption column it's produced this material we now have a collapse or a fountain of Ash and pumice coming out of the volcano flowing down the sides and creating a glowing avalanche of pumice and ash reaching this site then in a few minutes sigurðsson has calculated that vesuvius took 20 hours to eject all of its material in the resulting 4 meter thick pumice layer there are six Serge layers by measuring where they are Sigurdsson is at last able to show exactly when they happened the first was at 1:00 a.m. it's spread west and pulverized the town of Herculaneum at 2:15 a.m. there was a second bigger search at 6:30 a.m. 18 and a half hours after the eruption had first started an even larger third surge was generated luckily it ran out of energy just reaching the northern walls of Pompeii nevertheless it must have made the air thick with dust at 7:30 a.m. still choking and wheezing the inhabitants of Pompeii were overrun by search number four [Music] they were slain by an ashen dust-filled wind that swept over them at more than 200 kilometers an hour not only that it was also viciously hot sort of make our way gently on top of the we're into the pumice ball we see that the search is actually a very thin layer search number four it's only about five to ten centimeters in thickness but this search and the subsequent search over here are the the deposits that contain all of the human remains or almost all of the human remains in pompeii in addition they contain building material that was carried along in the inserts and that is now being preserved over here to my right you see several of the bodies of the people that were suffocated index fixated in the search because of the very high heat and searing high temperatures and being choked essentially on inhaling the hot ash and dusty air so this is one of these excellent sites where we can see the relationship between the volcanic processes the generation of the hot search and how it the fact that the people demonstrating to us clearly what was the lethal agent of the eruption here in Pompeii there was the fourth search in fact there is strong evidence that the pyroclastic surge was at least 100 degrees Celsius hot enough to boil water lapping by recording the temperature around the victims must have reached rather high levels why do I think the temperature was that high because we didn't find any bacteria in the soil surrounding the victims but we found bacteria in the natural cavities of the bone remains of the victims this means that the temperature was hot enough to boil and sterilize the soil the victims of pompeii had a horrible death a thick red-hot hurricane roared in their faces like a jet blast it seared their skin and filled the insides of their mouths noses and lungs with scalding dust that is why many look like they are sleeping they fell to the ground struggling in vain to shield themselves from the hellish burning wind but as quickly as it came the surge disappeared leaving its victims to die of their burns struggling to breathe it's very humbling for me to see this as a scientist I can come distance myself from it to some extent but then again I'm reminded by the number of colleagues that I've had and friends who died in surges like this in pyroclastic flows it's also reminds me of scenes I saw when I was working in Mexico in 1982 two days after the eruption of algae John where I 18 hundred people were killed in surges of this sort and I had the unpleasant experience of of seeing the bodies interred from that event so it's a horrible sight only a handful of volcanoes every century generate an eruption column few of those cause pyroclastic surge glands even fewer are ever captured on film during the 1997 eruption of Montserrat a small surge was created typically it was fast hot and devastated everything in its path with little warning it killed 20 people this is what killed the people of Pompeii it should have been the end but Sigurdsson has found one massive final surge far deadlier than all the rest at 8 a.m. it swept down the mountain through Herculaneum through Pompeii and out into the countryside beyond many who had fled the town and thought they had escaped were caught up in Vesuvius final deadly breath in fact the outer fringes reached the beach at stabby I wear prinnies uncle was trapped again his account exactly matches seiga-san's geological data the flames and smell of sulfur which gave warning of the approaching fire drove the others to take flight and roused him to stand up he stood and in suddenly collapsed I imagine because the dense fumes choked his breathing by blocking his windpipe which was constitutionally weak and narrow and often inflamed when daylight returned on the 26th two days after the last day he had seen his body was found intact and uninjured still fully clothed and looking more like sleep and death news of his uncle's misfortune no doubt came from sailors and slaves who had been far enough away to survive the vestigial effects of the last surge Pliny the Younger narrowly missed being overwhelmed by the massive cloud himself it had traveled 30 kilometers across the Bay of Naples looking like a black tidal wave and hit the headland of my sea gnome just as it ran out of energy people bewail their own fate all that of their relatives and there were some who prayed for death in their terror of dying many sought the aid of the gods but still more imagined there were no gods left and that the universe was plunged into eternal darkness for evermore [Music] the complete devastation inside Pompeii but also the horrors found outside its walls lead to the suspicion that many many more of the refugees must have died while fleeing on the roads and on the beaches [Music] the area covered by the final surge cloud is so unusually vast that only 1% of it has been excavated [Music] in fact no matter where the archaeologists dig they always find bodies looking for a stylist to the south of Pompeii there was the river port and another chance to escape could be to get to the river port take a boat and leave their excavations there at the end of the 19th century in the actual river now that area which we call Meridian Asia is it gained under excavation by the superintendent of Pompeii and more than 80 bodies have been recovered which means that they probably had already fled Pompeii all the surrounding area and had taken shelter in that area thus discovery of bodies far outside pompeii suggests a huge death toll seiga-san's prediction is that although 1,000 have been found 10 times that died half the population 10,000 people failed to escape the final pyroclastic surge so the big question is where are all the thousands of bodies are the Pompeians my suspicion is that they're down south south of the city south outside the city walls buried underneath the pyroclastic flows the searches in the region of the Sarno Valley the region where the Sarno River flows now it's a region that is now fairly densely inhabited it's a region where there probably will not be a lot of archaeological excavation in the future because of dense population and but if we want to find out more about the fate of the Pompeians I think that's where we should look not in the city but outside [Music] pliny does not tell us if most Pompeians lived or died subsequent Roman writers make little mention of them it is known that the emperor Titus spent a fortune in redevelopment aid for the area [Music] but the material that buried them and their bones tells us that they suffered one of the rarest and deadliest of all volcanic phenomena [Music] a hot pyroclastic surge that choked and burnt them as a result of the collapse of one of the biggest eruption columns of all time an eruption that few had a hope of surviving you [Music] you

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Length: 49min 52sec (2992 seconds)

Published: Thu Aug 23 2018